high cya, how to reduce it?

[gvon79]

Thank you for the quick reply! It's a 10k gallon fiberglass pool with a 1.5hp hayward superpump and sand filter. I currently use test strips that measures FC, pH and Alkalinity, and I get my water tested at the pool store every other week. The results I posted above were from the pool store. I would rather drain and refill to run lower chlorine levels, however I would be refilling with well water with high levels of iron, so I'm undecided on the best approach right now.

[Watermom]

Well water presents a whole other set of problems. Before you decide, go and read some of the posts in the Stains and Metal Matters section of the forum. A lot of people using well water have a lot of problems. Think about it and then come ask questions if you need to before deciding. Any possibility of trucking in water?

EDIT -- I'm not sure, but I think you may have to log out to be able to see that Metals section of the forum. Try it first while logged in but if that doesn't work, log out and try again.

[PoolDoc]

Hi Gvon;

3 options:

#1 - drain 2/3 of your pool and refill. Risky with an AG pool or a concrete pool if the water table is high; impossible on a vinyl pool without special preparations. PLUS, then you have to refill with iron contaminated water and deal with all that.

#2 - use a sodium bromide (Yellow Treat, other products) to 'de-stabilize' a small portion of your chlorine and turn it into bromine. The downside is that, not only will this consume some chlorine now, but it will result in much higher chlorine consumption over the next few weeks, even after the algae is gone.

#3 - use the Best Guess Chart to run a high chlorine pool. You'll need to get a DPD-FAS testkit, to do this, since only these kits can test the high levels of chlorine you'll have accurately. The upside of this is that you'll be able to chlorinate just 1 or 2x weekly. BTW, there is no really danger to high chlorine + high stabilizer in an outdoor pool.

Since you already have algae my suggestion would be the following:

1. Order a DPD-FAS kit (Amazon link below)
2. Purchase an cheap OTO/phenol red kit at Kmart, Lowes, etc. and use it, for now. Goofy strips produce unreliable readings, even when read by the dealer gizmo.
3. Dose with 2 gallons of plain 6% household bleach as soon as possible. (Doesn't have to be in the evening, since your CYA is so high.)
4. Go by a pool dealer, if you can, and purchase a sodium bromide based granular algae product. Use ONLY 1/4 of the recommended dose!
5. Use the OTO test kit and bleach to maintain a DARK yellow chlorine level (~10 ppm)
6. Once you get the DPD-FAS kit, if you still have algae, gradually increment your chlorine level up, till you reach 25 ppm OR the algae is gone.

Ben